FIGURE 3.

The mechanism by which TNF-α and IL-1β regulate MMP-3 expression in OA. This figure presented three pathways (NF-κb pathway, MAPK pathway, and PI3K/Akt pathway) that have been mentioned a lot when discussing the regulation of MMP-3 expression. TNF-α can bind to its traditional receptor TNFRI or non-classic receptor TNFRII and pass the signal through both NF-κb pathway. The transcriptional factor NF-κb could bind to the promoter of MMP3 gene and regulate MMP-3 expression. The binding of TNF-α and its receptors could also activate the TAK1 and then pass the signal through MAPK pathway. IL-1β could bind to its receptor and regulate MMP-3 expression through PI3K/Akt pathway.